Someone who is perspicacious notices, realizes, and understands things quickly. [formal]
...one of the most perspicacious and perceptive historians of that period.
Synonyms: perceptive, aware, sharp, keen
perspicacity (pɜːʳspɪkæsɪti ) uncountable noun Channel 4's overseas buyers have foreseen the audience demand with their usual perspicacity.
Synonyms: insight, discrimination, penetration, acumen